Pyloric stenosis

Pyloric stenosis is when the passage between the stomach and small bowel (pylorus) becomes narrower. This page explains pyloric stenosis, how it is treated and what to expect when your child comes to Great Ormond Street Hospital (GOSH) for assessment and treatment.

The pylorus passage is made up of muscle, which seems to become thicker than usual, closing up the inside of the passage. This stops milk or food passing into the bowel to be digested.

Medical conditions - Pyloric stenosis

What are the symptoms of pyloric stenosis?

In most cases, a baby with pyloric stenosis will begin bringing up small amounts of milk after feeding. Over a few days this will become worse until the baby can no longer keep any milk down. This vomiting may become so forceful that the milk may be projected for several feet out of the baby’s mouth. This is called projectile vomiting.

As the milk is lying in the acid in the stomach, it can curdle and become yellow in colour. This also reduces the amount of faeces (poo) passed, as little or no food is reaching the bowel.

If the condition is not treated, the baby will become dehydrated and not gain weight. Signs of dehydration include lethargy, wet nappies less frequently than normal and the soft spot (fontanel) on the top of the head may be sunken.

What causes pyloric stenosis and how common is it?

Pyloric stenosis is a fairly common reason for babies needing an operation and usually develops around six weeks after birth. We do not know exactly why pyloric stenosis develops, but it tends to affect more boys than girls, and seems to run in families too.

How is pyloric stenosis diagnosed?

The thickened pyloric muscle can be felt, especially during feeding, as a small, hard lump on the right side of the baby’s stomach. The muscles around the stomach can sometimes be seen straining, moving from left to right as they try to push milk through the pylorus.

Your child’s doctor will ask you lots of questions and may want to examine your baby during a feed to observe any vomiting.

Sometimes the doctors may want to confirm the diagnosis using tests and scans. These can include an ultrasound scan, like the ones used in pregnancy, to get a picture of the thickened muscle.

How is pyloric stenosis treated?

Pyloric stenosis is usually treated in an operation under general anaesthetic, lasting about 30 minutes. The operation is called a pyloromyotomy. Most are carried out using keyhole surgery (laparoscopically) but occasionally open surgery is suggested.

The effects of pyloric stenosis, like dehydration due to the vomiting, can become serious quite quickly in children, and so there are no alternatives to the operation.

What happens before the operation?

Your child will usually be transferred to GOSH from your local hospital.

If your child is dehydrated, he or she will need a ‘drip’ of fluids for a while before the operation. This will make sure that your child’s blood contains the right balance of salts and minerals, and treats the dehydration. Your child will have the operation once his or her blood test results are normal. 

They will also need a nasogastric tube, which is passed up the nose, down the food-pipe and into the stomach. This will drain off the stomach contents before the operation.

Your child’s surgeon will explain the operation in detail, discuss any worries you may have and ask your permission for the operation by asking you to sign a consent form. An anaesthetist will also see you to explain about your child’s anaesthetic in more detail. If your child has any medical problems, such as allergies, please tell the doctors.

What does the operation involve?

While your child is under general anaesthetic, the surgeon will cut through some of the thickened muscle, which widens the passage so that milk and food can pass into the bowel to be digested. If the operation was carried out using keyhole surgery, your child will have three small incisions in the abdomen, which will be closed with dissolvable stitches and skin glue. If your child has had open surgery, there will be a larger incision by the tummy button, closed with dissolvable stitches, Steri-strips®, which are like strong sticking plasters, and skin glue. 

Are there any risks?

All surgery carries a small risk of bleeding during or after the operation. There is a chance that the lining of the bowel could be damaged during the operation, but this is rare and will be stitched closed during the same operation. Every anaesthetic carries a risk of complications but this is very small.

What happens afterwards?

Your child will come back to the ward to recover. He or she will have been given pain relief during and after the operation. For the first few hours, your child will continue to have fluids through the drip so that the stomach and bowel can start to heal. After six hours or so, we will start to feed your child, starting with small amounts, and increasing the amount as he or she tolerates it. Your child may still have some vomiting but this will improve as the digestive system recovers from the operation. Your child will be able to go home once he or she is feeding well.

When you get home

Your child’s abdomen may feel sore for a while after the operation, but wearing loose clothes can help. Your child will need to have regular pain relief such as paracetamol for at least three days so please make sure that you have some at home.

The stitches used during the operation will dissolve on their own so there is no need to have them removed. If possible, keep the operation site clean and dry for two to three days, to allow the operation site heal properly. When your child has a bath, do not soak the area until the operation site has settled down.

You will usually need to come back to hospital for an outpatient appointment after the operation. We will send you the appointment date in the post.

You should call your family doctor (GP) or the ward if:

  • your child is in a lot of pain and pain relief does not seem to help

  • your child is not keeping any fluids down or has signs of dehydration

  • your child has a high temperature of 37.5°C or higher, and paracetamol does not bring it down

  • the operation site is red or inflamed, and feels hotter than the surrounding skin

  • there is any oozing from the operation site

  • your child continues to vomit or bring up milk.

What is the outlook for children with pyloric stenosis?

Most pyloric stenosis operations are successful, with the immediate effect of reducing or stopping completely any vomiting after feeds.

Compiled by: 
The General Surgery department in collaboration with the Child and Family Information Group.
Last review date: 
November 2015